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Tech Tip: Answered Webbing over a sharp edge, Redundancy

Discussion in 'Tech Tips and Gear' started by ratagonia, Jul 1, 2020.

  1. ratagonia

    ratagonia

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    Some talk lately about rigging webbing off an anchor when it goes over a sharp edge. Best practice?

    In A, we see a loop of webbing around the anchor, over the edge with a knot. Two strands cross the edge, more robust than one, but there is no redundancy in the system. If one piece cuts over the edge, the anchor fails.

    Rig1.

    In B. we have much the same thing, but with the knot moved above the sharp edge. If one strand of webbing cuts, then the anchor fails. No redundancy.

    Rig2.

    In C. we have one knot above and one knot below the edge, and now we have redundancy. For this illustration, I show one of the strands between the knots being slack - so we have a utilized strand, perhaps sacrificial, and a backup strand, rather than equalized strands that would share the load.

    Rig3.

    In D. we can see the same redundancy crossing the sharp edge, with a single strand of webbing going back to the anchor.
    Rig4.
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  2. Brian in SLC

    Brian in SLC Brian in SLC

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    Here's another variation:

    slinganchor.

    The advantage of this is double strand for durabilty over an edge. Also, the entire webbing loop can be pulled around and inspected 360 degrees. The wear point can be changed between users at both the rapide interface as well as any edge and the anchor itself. Plus...its simple.

    A lot of ways to skin that cat...
    Rapterman, Jenny and ratagonia like this.
  3. RobbyB

    RobbyB

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    I like redundancy over sharp edges but I think i am missing something in examples C and D, why have you not equalized the strands? The scenario in my head goes: if the edge is sharp enough to cut a single strand, are you creating a potential cutting hazard by shock loading the back up strand on the same sharp edge?
  4. ratagonia

    ratagonia

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    If I put in 3 feet of slack, that would be a big problem. The way I have it, one strand of webbing takes all the abuse while the second strand stays pristine. (The amount of slack is perhaps exaggerated for illustration purposes.) The pristine strand is able to handle the 3" shock load; rappels that cross sharpened chef knives excluded.

    If you have the two strands equalized, you get greater durability. With perfect equalization and equal wear, you actually do not get redundancy, because when one is ready to go, the other strand is too.

    Tom
    Last edited: Jul 3, 2020
    Rapterman, zul and RobbyB like this.
  5. Bootboy

    Bootboy Atwood Gear

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    The question is, why aren’t you using black webbing?
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  6. ratagonia

    ratagonia

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    For pictures? Because it does not photograph as well. Besides I have lots of colored webbing rescued from canyons that I use around the outfit for various utility functions, such as for photo models.

    t
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